Filled asphalt emulsions containing betaine emulsifier

ABSTRACT

Disclosed are filled oil-in-water asphalt emulsions which remain homogeneous for prolonged periods of time notwithstanding the presence of particulate filler that might be expected to break the emulsions. The emulsions contain asphalt dispersed as the discontinuous phase in an aqueous continuous phase, particulate filler, and one or more amphoteric emulsifiers selected from the group consisting of compounds of the formulas (a) and (b)R4-(OC3H6)0-1-(C(O)NH(CH2)1-3)0-1-N(Z1) (Z2)0-1-ZCOOX (a)R4-(OC3H6)0-1(C(O)NH(CH2)1-3)0-1-N(Z1) (Z2)0-1-ZSO3XH(b)wherein R4 is C4-24 alkyl or alkylene, f is 1-6, is -H or a cation, Z is (CH2)f, CH2CHOHCH2, or CH2CH2OCH2CH2, and Z1 and Z2 are CfH2f+1 or CfH2fOH, or in (a) Z1 can be -ZCOOX. The emulsions are useful for example in pavement and driveway coatings, pipe sealers, and vehicular undercoatings.

This application is a continuation-in-part of our previous application Ser. No. 08/409,663, field Mar. 24, 1995, now U.S. Pat. No. 5,558,702.

BACKGROUND OF THE INVENTION

The present invention relates to aqueous emulsions of the type used in pavements or coatings, containing asphalt or coal tar, and in particular to aqueous asphalt emulsions of the oil-in-water type wherein the asphalt component is the discontinuous phase and the aqueous vehicle is the continuous phase. More particularly, the present invention relates to aqueous emulsions of asphalt that can be combined with fillers such as clay, sand and/or fibers (such as fiberglass and/or cotton), and in some cases modified with polymerized materials such as rubber, latex or SBR-type polymers. Such filled emulsions are typically used for applying sealing coatings to driveways, parking lots, pipes, and the like.

Asphalt is conventionally recognized in this field as a dark brown to black cementitious material in which the predominating constituents are bitumens that occur in nature or are obtained in the fractionation of petroleum. Asphalt characteristically contains very high molecular weight hydrocarbons soluble in some hydrophobic solvents. Bitumen is generically known as a class of black or dark-cementitious substances, natural or manufactured, composed principally of high molecular weight hydrocarbons.

Asphalts have been known for many years in various naturally-occurring types, but more and more conventionally asphalts are obtained as a very high molecular weight fraction obtained through the refining or fractionation of petroleum feed streams. In some cases these petroleum fractions are chemically processed prior to or after fractionation; and emulsions made with the resulting treated asphalts are also the subject of this application.

Asphalt is useful in its ability, especially when combined with a fine particulate filler, to form a continuous, highly water-impervious film or coating when applied for instance to roofs, and other exterior surfaces such as driveways, sidewalks, roadways, pipes, as well as a coating for rustproofing, sound deadening or thermal insulation such as might be used for vehicular undercoatings; and the like.

Coal tars and fractionated coal tars are currently used in such applications, as emulsions and particularly as filled emulsions. The present invention can be considered applicable to the formation of such filled emulsions of coal tar and coal tar derivatives as well as to filled emulsions of asphalt.

Historically, coal tar and derivatives thereof have been incorporated into filled emulsions as the primary asphalt-like material. Filled coal tar emulsions are easily made using any of various surfactants. However, coal tar and its derivatives have become suspected as possibly carcinogenic, so avoiding their use has become desirable. Identifying satisfactory asphalt emulsions which are free of coal tar and coal tar derivatives is thus one of the principal objectives of the present invention.

The task of emulsifying asphalt and keeping it emulsified as a uniform dispersion of asphalt in the water in the presence of filler material, affording easy formulation of the final filled emulsion product, and at the same time obtaining the emulsion in a form which resists premature breaking, has been notoriously challenging. The components of the emulsifying system have to permit formation of the emulsion as desired prior to application of the emulsion to the particular surface. Once the emulsion has been applied and the water has evaporated, the components of the emulsifier system remain behind yet must not be permitted to re-emulsify the asphalt upon subsequent exposure to water. In addition, it is conventional practice to manufacture emulsion in large batches, comprising hundreds or even thousands of gallons, for bulk sales or from which individual consumer-sized quantities of the emulsion are dispensed for retail sale and use at a later date. Unfortunately, cationic and many anionic emulsifiers do not permit formation of stable filled asphalt emulsions which satisfy all of these requirements.

The stability of the emulsion before use, and the rapid curing of the emulsion after application, are particularly critical for packaged products sold to consumers but are also important for bulk products sold to contractors and large-scale applicators. The ability to formulate the emulsions, particularly on such large scale, is vulnerable to variations in the constitution of the water used to formulate the emulsion, and particularly vulnerable to the presence of dissolved salts which when present are known as "hardness" of the water. These salts can interfere with the ability to establish the desired emulsion, either through co-acting with the components of the emulsifying system, or otherwise for instance by undesirably altering the ionic strength of the aqueous phase of the emulsion.

The stability and curing behavior of the asphalt emulsion are particularly sensitive to the presence of solids added to the emulsion to form a filled emulsion product. These properties are also sensitive to the amount of such solids and to their identity.

It is also advantageous in some cases to produce a filled emulsion that is thixotropic. This thixotropic, or shear thinning, property minimizes splashing and pooling of the emulsion in low spots while enabling application of a desired thickness as is desirable in pavement and driveway sealers. In spray applications such as vehicular undercoatings or pipe coatings the thixotropic character minimizes runoff or dripping while allowing effective spraying.

It is thus an object of the invention to identify emulsifiers for the formation of asphalt emulsions, which are not adversely affected by the presence of solids used to produce filled products.

It is also an object of the invention to identify emulsifying agents for use in formulating asphalt emulsions, which resist premature "breaking" of the emulsion while in storage prior to application. It is furthermore desirable to formulate asphalt emulsions with components that are easily available and relatively inexpensive, and which as well do not adversely affect the quality of the film or coating formed following application of the asphalt emulsion.

The present invention satisfies these objects as well as others that will be apparent herein.

BRIEF SUMMARY OF THE INVENTION

One aspect of the present invention is a storage-stable oil-in-water asphalt emulsion, comprising (A) water as the continuous phase;

(B) one or more amphoteric emulsifiers, particularly those of formula (a), (b)

    R.sup.4 --(OC.sub.3 H.sub.6).sub.0-1 --(C(O)NH(CH.sub.2).sub.1-3).sub.0-1 --N(Z.sup.1) (Z.sup.2).sub.0-1 --ZCOOX                    (a)

    R.sup.4 --(OC.sub.3 H.sub.6).sub.0-1 --(C(O)NH(CH.sub.2).sub.1-3).sub.0-1 --N(Z.sup.1) (Z.sup.2).sub.0-1 --ZSO.sub.3 X              (b)

wherein X is --H or a cation such as sodium, calcium, potassium, lithium or ammonium, or an amine of the formula --N⁺ H(C₁₋₂₀ alkyl)₂ or --N⁺ H₂ (C₁₋₂₀ alkyl), R⁴ is straight or branched alkyl or alkylene, or cyclic or heterocyclic aromatic which is optionally substituted with alkyl, and contains 4 to 40 carbon atoms and 0-5 carbon-carbon double bonds, Z¹ and Z² are independently of each other H, C_(f) H_(2f+1) or C_(f) H_(2f) OH wherein f is 1 to 6 and preferably 1, 2 or 3 or, in formula (a), one of Z¹ and Z² can be --ZCOOX, and Z is (CH₂)_(f), CH₂ CH₂ OCH₂ CH₂, or CH₂ CHOHCH₂ ;

(C) asphalt, comprising a discontinuous phase uniformly dispersed in said emulsion; and

(D) finely divided particulate filler uniformly distributed throughout said emulsion.

From evaluations of many emulsifiers, and finding little success, it is quite surprising to have found that emulsions in accordance with this invention form storage-stable filled emulsions, without loss of the emulsion and without loss of stability or curing properties. Additionally, it was very surprising to find that a broad range of amphoteric emulsifiers produce stable filled emulsions that met the desired properties set forth herein.

Another aspect of the present invention is a method of making an oil-in-water asphalt emulsion, comprising combining asphalt, an aqueous continuous phase, and one or more emulsifiers selected from the group consisting of compounds of the formulas (a) and (b) as defined above, and finely divided particulate filler, in any sequence under emulsifying conditions effective to form an emulsion which exhibits long-term phase stability.

The terms "storage-stable" and "long-term phase stability" are used herein in their conventional senses, as meaning that the emulsions of the present invention remain as emulsions, i.e. liquid, essentially indefinitely; that the liquid remains homogeneous essentially indefinitely; and that the particulate filler, once dispersed throughout the emulsion, exhibits greatly reduced tendency to separate out of the emulsion.

DETAILED DESCRIPTION OF THE INVENTION

It has now, quite unexpectedly, been found that emulsifying the asphalt with any of the aforementioned emulsifiers of formulas (a) and/or (b) affords uniform dispersibility of the asphalt in water and obtains an emulsion which resists premature breaking when fillers are added to the emulsion. The system forms an emulsion which prior to application is stable, at room temperature conditions, for a reasonably long period of time. The emulsion is able to withstand mixing with fine particulate matter such as clay, fibers, or sand without breaking (becoming two distinct phases of oil and water). The resulting emulsion mix, sometimes called a "filled emulsion", is compatible and stable for a reasonably long period of time.

By correct choice of the emulsifier, and/or incorporation one or more anionic and/or nonionic emulsifiers, the flow properties of the resulting emulsion can be varied anywhere from a relatively thin free flowing liquid to a very thick thixotropic paste. Once the filled emulsion is applied, for example on the surfaces of driveways, parking lots, piping, or in crack filling application, it cures in a reasonably short time with associated water evaporation. This discovery furthermore permits one to formulate the asphalt emulsion with components that are easily available and relatively inexpensive.

The asphalt (or bitumen) employed in this invention can be either a naturally-occurring asphalt or a manufactured asphalt produced for instance by refining petroleum. It can be a coal tar or coal tar derivative. It can be other heavy bitumenous material as well as heavy organic residuums. Naturally-occurring asphalts suitable for use in this invention include, for example, lake asphalts, rock asphalts and the like. Suitable manufactured asphalts include, for example, straight-run asphalts, propane asphalts, air-blown asphalts, thermal asphalts, blended asphalts, and the like. As used herein, the term "asphalt" includes materials sometimes referred to as "bitumen". A further description of asphalt useful in this invention may be found in the "Encyclopedia of Chemical Technology", Volume 3, at pp. 284-327, the content of which is hereby incorporated herein by reference.

Asphalts preferred for use in this invention have an initial viscosity (i.e. the viscosity prior to emulsification) at 60° C. of from about 100 to about 20,000 poise, although asphalts having higher or lower viscosities can also be useful. The viscosity may be determined by the procedures described in ASTM Test Method D2171. The asphalt quality can also be described by hardness or penetration number. Typically, asphalts in the penetration range of 5 to 400 and preferably 20 to 150 are used, but asphalts with higher or lower values can be used. For some applications, such as driveway sealers, the preference is for harder asphalts (lower penetration number) so that the asphalt can resist softening by drippings of petroleum based products.

Referring to formulas (a) and (b), the present invention has been found to form stable filled asphalt emulsions employing any of a broad range of amphoteric emulsifiers, particularly including but not limited to amphoteric compounds which correspond to either of those formulas. Formulas (a) and (b) embrace betaines, sulfobetaines (sultaines), glycinates and propionates, which are commercially available and/or can readily be synthesized.

The results described herein indicate that any amphoteric compound is likely to form successfully a filled asphalt emulsion. Examples of preferred amphoteric emulsifiers include fatty betaines such as lauryl dimethyl betaine (e.g. REWOTERIC® AM-DML-35)(this and all other REWOTERIC®-branded compounds are marketed by Witco Corp.) and N-lauryl-beta-iminopropionic acid, mono-sodium salt (e.g. REWOTERIC® AM-LP); glycinates such as N-cocoylamidoethyl-N-(2-hydroxyethyl)-N-carboxymethyl glycine, disodium salt (e.g. REWOTERIC® AM-2C-W) and the N-lauroyl analog thereof (e.g. REWOTERIC®-AM-B-15); propionates such as sodium cocoamphopropionate (e.g. REWOTERIC®AM-KSF-40); and sulfobetaines such as lauryl hydroxy sultaine (e.g. REWOTERIC® AM-HC) and cocamidopropyl hydroxysultaine (e.g. REWOTERIC® AM-CAS).

Thus, preferred Z groups include --CH₂ -- and --(CH₂)₂ --. Preferred compounds include those wherein one or both, more preferably both, of Z¹ and Z² are --CH₃ ; or Z¹ is --CH₂ COONa and Z² is --CH₂ CH₂ OH.

Preferred R⁴ groups include alkyl and alkylene radicals derived from fatty acids. Other preferred R⁴ groups include benzyl, alkyl-substituted benzyl, and saturated and unsaturated 5-member and 6-member rings containing as the ring atoms exclusively carbon, or carbon and 1 or 2 nitrogen atoms, such as piperazine and alkyl-substituted piperazine. R⁴ can contain 4 to 40 carbon atoms, preferably 10 to 24 carbon atoms and more preferably 12 to 18 carbon atoms.

It should be recognized that, if desired, amounts of other emulsifying components may be present together with the one or more compounds of the foregoing formulas (a) and/or (b). Thus, while the advantages attributed to the present invention can be realized by employing solely one or a mixture of the compounds of the foregoing formulas (a) and/or (b), as the emulsifying components, the scope of the present invention is not confined to those systems which exclude the presence of other emulsifying agents so long as they are compatible with the emulsifying capabilities of the compounds described herein. Indeed, the compatibility of these compounds when used together with other emulsifying agents, while still being able to maintain a storage-stable emulsion, is another valuable and unexpected aspect of this invention.

For instance, one may include one or more compounds of the formula (Ia), (Ib)

    (R.sup.1 CH(OH)--(CH.sub.2).sub.m SO.sub.3).sub.i X        (Ia)

    (R.sup.1 CH═CH(CH.sub.2).sub.m-1 SO.sub.3).sub.1 X     (Ib)

and mixtures thereof, wherein R¹ contains 6 to 40 carbon atoms and is straight or branched aliphatic, aromatic, alkyl-aromatic, aromatic-alkyl, or alkyl-aromatic-alkyl, m is 1-10, X is as defined above, and i is 1 or more and is the valence of X.

Preferred R¹ groups include straight and branched alkyl groups containing 9-25, and preferably 15-17, carbon atoms. Preferred R¹ groups containing an aromatic moiety include these wherein the aromatic moiety is phenyl. Other aromatic moieties include naphthalene, indanyl and indenyl. Examples of groups with an aromatic moiety include phenyl, alkyl-substituted phenyl, benzyl and alkyl-substituted benzyl. In formulas (Ia) and Ib), m is 1-10 and preferably 2-4.

Preferred compounds include those known generically as olefin sulfonates, which are mixtures of long chain sulfonate salts prepared by sulfonation of long chain olefins. Because of the nature of the sulfonation process, the olefin sulfonates generally comprise mixtures of alkene sulfonates and hydroxy alkane sulfonates. Particularly preferred olefin sulfonates include, but are not limited to, alpha-olefin sulfonates.

Preferred examples of these olefin sulfonates useful in the present invention are those sold by Witco Corporation under the name "Witconate AOS", and "Witconate AOS-PC".

The emulsions useful in the present invention can also include one or more carboxylated nonionics of the formula (II):

    R.sup.2 O--(AlkO).sub.c CH.sub.2 COOX                      (II)

wherein X is defined above. In formula (II), R² contains 6 to 40 carbon atoms and can be an alkyl group which can be straight or branched. Examples of such alkyl groups include lauryl, oleyl, C₁₂ -C₁₅, tetradecyl, tridecyl, and ethylhexyl. Preferred R² groups include any of those described above with respect to preferred R¹ groups. A preferred example of R² as a substituted phenyl group is nonyl phenol. Each (AlkO) group can be ethoxy, propoxy or butoxy. The preferred (AlkO)_(c) can be a chain of randomly assembled ethoxy and propoxy units, a homo-oligomer of only ethoxy or only propoxy units, a block copolymer containing one or more blocks of repeating ethoxy units and one or more blocks of repeating propoxy units, or other combinations of ethoxy and propoxy. As noted, the total number c of alkoxy units is 1-200, preferably 1-60 and more preferably 5-20.

The emulsions of the present invention can also comprise one or more alkyl aryl sulfonates of the formula (III):

    ((R.sup.3).sub.k --A--SO.sub.3).sub.i X                    (III)

wherein i and X are as defined hereinabove. Each R³ group contains 6 to 40 carbon atoms. Preferred R³ groups include straight or branched alkyl groups containing to 6 to 40, preferably 6 to 24, and more preferably 12 to 14, carbon atoms. Other preferred R³ groups include aromatic-alkyl, such as benzyl or phenethyl, it being noted that R³ should be selected so that an aromatic moiety is not bonded directly to A. Preferably A is a monocyclic or polycyclic aromatic group, preferably phenyl or naphthyl and more preferably phenyl, and k is 1, 2 or 3. Preferably, k is 1.

The filled emulsions of the present invention also include a filler component which is composed of finely divided particulate material that does not react chemically with the other components. Examples include clay, synthetic or naturally occurring fibers, lime, sand and/or carbon black. The particle size distribution should be well below that of aggregate, such as that which is bound with asphalt to create paving material. The particle size can be that of conventional fillers currently used in coal tar asphalt emulsions, but is preferably, generally about 0.5 microns to about 0.01 millimeters up to about 2 or even 3-5 millimeters.

The emulsions of the present invention will of course also contain water, as the continuous phase, and on occasion water may be added along with the particulate fillers. The emulsions may contain other components that can be present in filled asphalt emulsions without interfering with the properties of the filled emulsions of the present invention. Such optional additional ingredients particularly include but are not limited to fuel oil, kerosene, antistrip agents, latex or other polymers compatible with the emulsion, and agents such as thixotropicity agents to adjust and control the viscosity of the final product.

When the intended end use is a product having a relatively less viscous nature, such as for driveway sealing, the viscosity can be adjusted as desired by addition of an anionic or nonionic emulsifier (or both) to the amphoteric emulsifier that is present.

The relative amounts of the asphalt, the aqueous phase, and the emulsifying component, are of course a function of the fact that the product (whether filled or unfilled) must take the form of an oil-in-water emulsion of the asphalt in the aqueous phase as the continuous phase. As such, then, the permissible amounts of the asphalt, water, and emulsifying components in the unfilled emulsion can vary within relatively large ranges, the asphalt comprising about 5 to about 95 percent by weight of the emulsion, and preferably up to 85 percent by weight of the emulsion, and more preferably the narrower range of about 50 to about 70 weight percent of the emulsion.

The filled emulsion contains from about 5 or 10 to about 90 percent by weight of the particulate filler, preferably about 10 to about 70 percent by weight, and more preferably about 10 to about 30 percent by weight of the filled emulsion. The emulsifying component, as the total effective amount of compounds of formulas (a), (b), and (if present) of formulas (Ia), (Ib), (II) and (III), will generally comprise (but is not restricted to) about 0.1 to about 5.0 percent weight of the filled emulsion, and preferably comprise the narrower range of about 0.2 or 0.5 to about 2.0 weight percent of the emulsion. In this specification and the claims appended hereto, all emulsifier and surfactant contents are expressed on an active-surfactant basis. The water generally comprises but is not restricted to about 20 to about 70 percent by weight of the filled emulsion, or more narrowly about 30 to about 50 weight percent of the emulsion.

The pH of the emulsion can be about 1 to about 14, but is preferably about 7 to about 10. If pH adjustment is necessary during formulation, it can be accomplished by addition of small but effective amounts of base such as sodium hydroxide or acid such as sulfonic acid.

Preparation of the emulsion involves relatively straightforward application of conventional emulsification technology. The asphalt when emulsified should preferably be in the form of very fine droplets or particles having a diameter on the order of about 0.5 to about 50 microns, preferably about 5 to about 10 microns. To obtain particle sizes that permit emulsification of the asphalt, the asphalt component when formulated into the emulsion must be hot enough to be liquid but not so hot as to cause the aqueous phase to boil off, which obviously would break the emulsion.

Emulsification can be carried out in a mill of conventional design known to those of ordinary skill in this art, such as a colloid mill, which simultaneously intimately mixes the water, asphalt and emulsifying components using high shear. The emulsifying compounds used in the present invention can be added simultaneously with the water and the asphalt, or more preferably can be dissolved in the water prior to mixing with the asphalt.

The desired filled asphalt emulsion is made by mixing the filler(s), that is, fibers, clays, lime and/or sand and/or other additives, into the emulsion. The filler components and water may be pre-mixed to water-wet them and then added to the emulsion after it is formed. However, the filler components can be added per se, or pre-mixed with any other emulsion component, and combined with all the other components in the mill or thereafter.

Asphalt emulsions prepared in accordance with the present invention exhibit a number of advantageous properties, notably, emulsions formed with the compounds of the foregoing formulas (a) and/or (b) resist breaking to a superior and unexpected degree even when formulated with filling components, and even when made with water, including i.e. "hard" water, containing salts dissolved therein. In general, the emulsions prepared in accordance with the present invention resist generally "breaking" to a superior and unexpected degree compared to emulsions prepared with other emulsifying systems.

Another conspicuous advantage of the emulsions of the present invention is that they permit the formation of useful, stable asphalt emulsions while avoiding the use of coal tar and of products derived from coal tar. It is desirable to avoid the use of coal tar and its derivatives, as they have been implicated in recent years as suspected carcinogens. However, as discussed herein, the task of identifying suitable materials providing the valuable properties afforded by coal tar or its derivatives has not been achievable. The present invention, however, satisfies that significant objective.

The following examples are provided for purposes of illustration and are not intended to limit the scope of the present invention.

EXAMPLE 1

Asphalt emulsions were prepared by emulsifying asphalt in water with several different amphoteric emulsifiers of formula (IVa) or (IVb). The components and respective amounts were as follows; the pH was adjusted to the indicated value by adding sodium hydroxide:

    ______________________________________                                                    Use level as wt. %                                                  Emulsifier of emulsion   pH     Asphalt                                        ______________________________________                                         Cocamidopropyl                                                                            2.6           11     Ashland AC-20                                  dimethylbetaine                                                                Cocamidopropyl                                                                            2.6           11     Chevron AC-20                                  hydroxy sultaine                                                               Lauryl     2.6           11     Chevron AC-20                                  dimethyl betaine                                                               Disodium coco-                                                                            2.6           11     Chevron AC-20                                  amphodiacetate                                                                 ______________________________________                                    

Combining each of these emulsions with Sealer "A", at levels of about 70 wt. % Sealer "A" or higher at 120°-130° F., gave smooth, thick, homogeneous emulsions. When these products were spread out into films and cured, a smooth, continuous, durable layer formed in a short period of time.

COMPARATIVE EXAMPLES

Tests conducted with some other emulsifiers were unable to produce stable filled asphalt emulsions. These results demonstrated that the success of the particular selection of emulsifiers embodied in the present invention is quite unexpected. For instance, a typical anionic emulsifier such as tall oil fatty acids commonly used for manufacturing of rapid-medium set type asphalt emulsions at range of 0.4 to 0.6% use levels, did not produce a stable, filled asphalt emulsion, even at 0.6% and at 1.0% use level (by weight of the emulsion). The emulsifier solution pH was adjusted to 10.0 by adding NaOH. "AC-20" asphalt (Ashland) was used at 280° F. to manufacture the emulsion in a Charlotte G-5 colloidal emulsion mill. The resulting emulsion, after 24 hours storage at room temperature, was mixed with Sealer "A" defined in Table A, Example 1. The results were broken, incompatible emulsions.

Similar tests conducted with cationic emulsifiers, even at higher use levels, demonstrated that cationic emulsifiers could not form a stable emulsion containing as filler fine materials such as clay, lime, fiber, and sand used in driveway sealer application. Emulsion/Sealer "A" mixtures at 50:50 ratio formed incompatible, broken emulsions. 

What is claimed is:
 1. A storage-stable filled oil-in-water asphalt emulsion which exhibits long-term phase stability comprising(A) water as a continuous phase; (B) one or more amphoteric emulsifiers having the formula

    R.sup.4 --(OC.sub.3 H.sub.6).sub.0-1 (C(O)NH(CH.sub.2).sub.1-3).sub.0-1 --N(Z.sup.1) (Z.sup.2).sub.0-1 --ZCOOX

wherein X is --H, sodium, calcium, potassium, lithium, ammonium or an amine of the formula --N⁺ H(C₁₋₂₀ alkyl)₂ or --N⁺ H₂ (C₁₋₂₀ alkyl), R⁴ is straight or branched alkyl or alkylene or homocyclic or heterocyclic aromatic which is optionally substituted with alkyl and contains 4 to 40 carbon atoms and 0-5 carbon-carbon double bonds, Z¹ and Z² are independently of each other C_(f) H_(2f+1) or C_(f) H_(2f) OH, wherein f is 1 to 6, or one of Z¹ and Z² can be --ZCOOX, wherein Z is (CH₂)_(f), CH₂ CH₂ OCH₂ CH₂ or CH₂ CHOHCH₂ ; (C) asphalt, comprising a discontinuous phase uniformly dispersed in said emulsion; and (D) particulate filler which does not react with (A), (B) and/or (C) uniformly distributed throughout said emulsion.
 2. An emulsion in accordance with claim 1, wherein asphalt comprises about 5 to about 85 percent by weight of the emulsion.
 3. An emulsion in accordance with claim 1, wherein asphalt comprises about 50 to about 70 percent by weight of the emulsion.
 4. An emulsion in accordance with claim 1, wherein said one or more emulsifiers comprise about 0.1 to about 5 weight percent of the emulsion.
 5. An emulsion in accordance with claim 1, wherein said one or more emulsifiers comprise about 1 to about 2 weight percent of the emulsion.
 6. An emulsion in accordance with claim 1 wherein said filler comprises one or more materials selected from the group consisting of sand, fiber, clay, lime, and carbon black.
 7. An emulsion in accordance with claim 1 comprising at least one amphoteric emulsifier of formula (a) wherein Z is --CH₂ --.
 8. An emulsion in accordance with claim 7 comprising at least one amphoteric emulsifier of formula (a) wherein Z¹ and Z² are methyl, and Z is --CH₂ --.
 9. An emulsion in accordance with claim 8 comprising at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 4-24 carbon atoms and 0-5 carbon-carbon double bonds.
 10. An emulsion in accordance with claim 9 comprising at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 10-24 carbon atoms and 0-5 carbon-carbon double bonds.
 11. An emulsion in accordance with claim 9 comprising at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 6-18 carbon atoms and 0-5 carbon-carbon double bonds.
 12. An emulsion in accordance with claim 11 comprising one or more of cocamidopropyl dimethyl betaine, lauryl amidopropyl dimethyl betaine, cocodimethyl betaine, and lauryl dimethyl betaine.
 13. An emulsion in accordance with claim 7 comprising at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH.
 14. An emulsion in accordance with claim 13, comprising at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 4-24 carbon atoms and has 0-5 carbon-carbon double bonds.
 15. An emulsion in accordance with claim 14, comprising at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 10-24 carbon atoms and has 0-5 carbon-carbon double bonds.
 16. An emulsion in accordance with claim 14, comprising at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa and Z² is --CH₂ CH₂ OH, and R⁴ contains 6-18 carbon atoms and has 0-3 carbon-carbon double bonds.
 17. An emulsion in accordance with claim 13 comprising at least one amphoteric emulsifier selected from the group consisting of N-cocoylamidoethyl-N-(2-hydroxyethyl)-N-carboxymethyl glycine, N-lauroylamidoethyl-N-(2-hydroxyethyl)-N-carboxymethyl glycine, and the disodium salts thereof.
 18. An emulsion in accordance with claim 1 comprising at least one amphoteric emulsifier of formula (a) wherein Z is --(CH₂)₂ --.
 19. An emulsion in accordance with claim 18 comprising at least one emulsifier of formula (a) wherein Z is --(CH₂)₂ --, and Z¹ and Z² are methyl.
 20. An emulsion in accordance with claim 19 comprising at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 4-24 carbon atoms and 0-5 carbon-carbon double bonds.
 21. An emulsion in accordance with claim 20 comprising at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 10-24 carbon atoms and 0-5 carbon-carbon double bonds.
 22. An emulsion in accordance with claim 20 comprising at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 6-18 carbon atoms and 0-3 carbon-carbon double bonds.
 23. An emulsion in accordance with claim 1 comprising at least one amphoteric emulsifier selected from the group consisting of N-lauryl beta imino propionic acid, N-coco beta imino propionic acid, and monosodium salts thereof.
 24. A method of forming an oil-in-water asphalt emulsion comprising(a) forming a mixture of water, asphalt and one or more amphoteric emulsifiers having the formula

    R.sup.4 --(OC.sub.3 H.sub.6).sub.0-1 (C(O)NH(CH.sub.2).sub.1-3).sub.0-1 --N(Z.sup.1) (Z.sup.2).sub.0-1 --ZCOOX

wherein X is --H, sodium, calcium, potassium, lithium or ammonium or an amine of the formula --N⁺ H(C₁₋₂₀ alkyl)₂ or --N⁺ H₂ (C₁₋₂₀ alkyl), R⁴ is straight or branched alkyl or alkylene or homocyclic or heterocyclic aromatic which is optionally substituted with alkyl and contains 4 to 40 carbon atoms and 0-5 carbon-carbon double bonds, Z¹ and Z² are independently of each other C_(f) H_(2f+1) or C_(f) H_(2f) OH, wherein f is 1 to 6, or one of Z¹ and Z² can be --ZCOOX, wherein Z is (CH₂)_(f), CH₂ CH₂ OCH₂ CH₂ or CH₂ CHOHCH₂ and (b) emulsifying said mixture whereby an emulsion is formed in which said water is the continuous phase and said asphalt is a discontinuous phase uniformly dispersed in said emulsion, further comprising adding particulate filler that does not chemically react with said water, asphalt and/or amphoteric emulsifiers to said mixture before, during and/or after emulsification thereof, wherein said emulsion is a storage-stable oil-in-water asphalt emulsion having said particulate filler uniformly distributed throughout said emulsion, which emulsion exhibits long-term phase stability.
 25. A method in accordance with claim 24, wherein asphalt comprises about 5 to about 85 percent by weight of the emulsion.
 26. A method in accordance with claim 24, wherein asphalt comprises about 50 to about 70 percent by weight of the emulsion.
 27. A method in accordance with claim 24, wherein said one or more emulsifiers comprise about 0.1 to about 5 weight percent of the emulsion.
 28. A method in accordance with claim 24, wherein said one or more emulsifiers comprise about 1 to about 2 weight percent of the emulsion.
 29. A method in accordance with claim 24 wherein said filler comprises one or more materials selected from the group consisting of sand, fiber, clay, lime and carbon black.
 30. A method in accordance with claim 24 wherein said emulsion comprises at least one amphoteric emulsifier or formula (a) wherein Z is --CH₂ --.
 31. A method in accordance with claim 30 wherein said emulsion comprises at least one amphoteric emulsifier of formula (a) wherein Z¹ and Z² are methyl, and Z is --CH₂ --.
 32. A method in accordance with claim 31 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 4-24 carbon atoms and 0-5 carbon-carbon double bonds.
 33. A method in accordance with claim 32 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 10-24 carbon atoms and 0-5 carbon-carbon double bonds.
 34. A method in accordance with claim 32 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 6-18 carbon atoms and 0-5 carbon-carbon double bonds.
 35. A method in accordance with claim 34 wherein said emulsion comprises one or more of cocamidopropyl dimethyl betaine, lauryl amidopropyl dimethyl betaine, cocodimethyl betaine, and lauryl dimethyl betaine.
 36. A method in accordance with claim 30 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)₂ --, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH.
 37. A method in accordance with claim 36 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, wherein Z is --(CH₂)₂ --, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 4-24 carbon atoms and has 0-5 carbon-carbon double bonds.
 38. A method in accordance with claim 37 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, wherein Z is --(CH₂)₂ --, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 10-24 carbon atoms and has 0-5 carbon-carbon double bonds.
 39. A method in accordance with claim 37 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, wherein Z is --(CH₂)₂ --, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 6-18 carbon atoms and has 0-3 carbon-carbon double bonds.
 40. A method in accordance with claim 36 wherein said emulsion comprises at least one amphoteric emulsifier selected from the group consisting of N-cocoylamidoethyl-N-(2-hydroxyethyl)-N-carboxymethyl glycine, and the disodium salts thereof.
 41. A method in accordance with claim 24 wherein said emulsion comprises at least one amphoteric emulsifier of formula (a) wherein Z is --(CH₂)₂ --.
 42. A method in accordance with claim 41 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)₂ -- and Z¹ and Z² are methyl.
 43. A method in accordance with claim 42 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 4-24 carbon atoms and 0-5 carbon-carbon double bonds.
 44. A method in accordance with claim 43 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 10-24 carbon atoms and 0-5 carbon-carbon double bonds.
 45. A method in accordance with claim 43 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 6-18 carbon atoms and 0-3 carbon-carbon double bonds.
 46. A method in accordance with claim 24 wherein said emulsion comprises at least one amphoteric emulsifier selected from the group consisting of N-lauryl beta imino propionic acid, N-coco beta imino propionic acid, and monosodium salts thereof.
 47. A method of forming a continuous, highly water-impervious coating to a surface comprising (1) forming a storage-stable filled oil-in-water asphalt emulsion which exhibits long-term phase stability, said emulsion comprising(A) water as a continuous phase; (B) asphalt as a discontinuous phase uniformly dispersed in said emulsion; (C) particulate filler that does not chemically react with said water and said asphalt uniformly distributed throughout said emulsion; and (D) one or more amphoteric emulsifiers which are compounds of the formula

    R.sup.4 --(OC.sub.3 H.sub.6).sub.0-1 (C(O)NH(CH.sub.2).sub.1-3).sub.0-1 --N(Z.sup.1)(Z.sup.2).sub.0-1 --ZCOOX

wherein X is --H, sodium, calcium, potassium, lithium or ammonium or an amine of the formula --N⁺ H(C₁₋₂₀ alkyl)₂ or --N⁺ H₂ (C₁₋₂₀ alkyl), R⁴ is straight or branched alkyl or alkylene or homocyclic or heterocyclic aromatic which is optionally substituted with alkyl and contains 4 to 40 carbon atoms and 0-5 carbon-carbon double bonds, Z¹ and Z² are independently of each other C_(f) H_(2f+1) OH or C_(f) H_(2f) OH, wherein f is 1 to 6, or one of Z¹ and Z² can be --ZCOOX, wherein Z is (CH₂)_(f), CH₂ CH₂ OCH₂ CH₂ or CH₂ CHOHCH₂ ; and (2) coating a surface with said asphalt emulsion.
 48. A method in accordance with claim 47 wherein asphalt comprises about 5 to about 85 percent by weight of the emulsion.
 49. A method in accordance with claim 47, wherein asphalt comprises about 50 to 70 percent by weight of the emulsion.
 50. A method in accordance with claim 47, wherein said one or more emulsifiers comprise about 0.1 to about 5 weight percent of the emulsion.
 51. A method in accordance with claim 47, wherein said one or more emulsifiers comprise about 1 to about 2 weight percent of the emulsion.
 52. A method in accordance with claim 47 wherein said filler comprises one or more materials selected from the group consisting of sand, fiber, clay, lime, and carbon black.
 53. A method in accordance with claim 47 wherein said emulsion comprises at least one amphoteric emulsifier of formula (a) wherein Z is --CH₂ --.
 54. A method in accordance with claim 53 wherein said emulsion comprises at least one amphoteric emulsifier of formula (a) wherein Z¹ and Z² are methyl, and Z is --CH₂ --.
 55. A method in accordance with claim 54 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 4-24 carbon atoms and 0-5 carbon-carbon double bonds.
 56. A method in accordance with claim 55 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 10-24 carbon atoms and 0-5 carbon-carbon double bonds.
 57. A method in accordance with claim 55 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --CH₂ --, and R⁴ contains 6-18 carbon atoms and 0-5 carbon-carbon double bonds.
 58. A method in accordance with claim 57 wherein said emulsion comprises one or more of cocamidopropyl dimethyl betaine, lauryl amidopropyl dimethyl betaine, cocodimethyl betaine, and lauryl dimethyl betaine.
 59. A method in accordance with claim 53 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH.
 60. A method in accordance with claim 59, wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 4-24 carbon atoms and has 0-5 carbon-carbon double bonds.
 61. A method in accordance with claim 60 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 10-24 carbon atoms and has 0-5 carbon-carbon double bonds.
 62. A method in accordance with claim 60 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)--, Z¹ is --CH₂ COONa, and Z² is --CH₂ CH₂ OH, and R⁴ contains 6-18 carbon atoms and has 0-3 carbon-carbon double bonds.
 63. A method in accordance with claim 59 wherein said emulsion comprises at least one amphoteric emulsifier selected from the group consisting of N-cocoylamidoethyl-N-(2-hydroxyethyl)-N-carboxymethyl glycine, N-lauroylamidoethyl-N-(2-hydroxyethyl)-N-carboxymethyl glycine, and the disodium salts thereof.
 64. A method in accordance with claim 47 wherein said emulsion comprises at least one amphoteric emulsifier of formula (a) wherein Z is --(CH₂)₂ --.
 65. A method in accordance with claim 64 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z is --(CH₂)₂ --, and Z¹ and Z² are methyl.
 66. A method in accordance with claim 65 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 4-24 carbon atoms and 0-5 carbon-carbon double bonds.
 67. A method in accordance with claim 66 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 10-24 carbon atoms and 0-5 carbon-carbon double bonds.
 68. A method in accordance with claim 66 wherein said emulsion comprises at least one emulsifier of formula (a) wherein Z¹ and Z² are methyl, Z is --(CH₂)₂ --, and R⁴ contains 6-18 carbon atoms and 0-3 carbon-carbon double bonds.
 69. A method in accordance with claim 47 wherein said emulsion comprises at least one amphoteric emulsifier selected from the group consisting of N-lauryl beta imino propionic acid, N-coco beta imino propionic acid, and monosodium salts thereof. 